"On August 31, 1949, Louis Johnson, who was the United States’ Secretary of Defense, announced the creation of an Armed Forces Day to replace separate Army, Navy and Air Force Days. The event stemmed from the armed forces’ unification under one department – the Department of Defense. The Army, Navy and Air Force leagues adopted the newly formed day. The Marine Corps League declined to drop support for Marine Corps Day but supports Armed Forces Day too.

The first Armed Forces Day was celebrated on Saturday, May 20, 1950. The theme for that day was “Teamed for Defense”, which expressed the unification of all military forces under one government department. According to the U.S. Department of Defense, the day was designed to expand public understanding of what type of job was performed and the role of the military in civilian life.

Armed Forces Day was a day for the military to show "state-of-the-art" equipment to Americans. It was also a day to honor and acknowledge Americans in the armed forces. Parades, open houses, receptions and air shows were held at the inaugural Armed Forces Day. Armed Forces Day is still celebrated nationwide today and is part of Armed Forces Week."-  Source